Field of the Invention
The present invention relates to an electric-motor arrangement for a medical, in particular dental, hand piece. The electric-motor arrangement comprises an electric motor, in particular a small dental motor, that is to say an electric motor of compact design which is provided, in particular, for use in dental hand-held units. An electric-motor arrangement of this type is also called “dental motor” or “small dental motor” for short in the following text.
Related Technology
In particular, the invention relates to an electric-motor arrangement which is provided for being connected via a coupling to a medical, in particular to a dental hand piece and angular piece, also called “hand piece” for short in the following text, the hand piece being configured for receiving a rotatably mounted tool and, if the electric-motor arrangement is coupled to the hand piece as provided, it being possible for a torque which is generated by the electric-motor arrangement to be transmitted to the tool. A corresponding arrangement is known, for example, from DE 33 32 627 A1. Furthermore, it can be provided, in particular, that a supply hose is connected via a further coupling so as to lie opposite the hand piece, in relation to the electric-motor arrangement, which supply hose serves to supply the electric-motor arrangement or the hand piece and has, for example, medium lines, by which media such as air and/or water can be transported in order to form a spray. A power line and/or a light cable can also be arranged in the supply hose.
In an electric-motor arrangement of this type, it is desirable that the rotor of the electric motor vibrates as little as possible in the operating state. A long service life of the electric motor is also desirable. Therefore, mounting of the rotor as exactly as possible is usually aimed for without any alignment errors, in particular in the case of a fast-running dental motor.
The prior art has disclosed a corresponding electric-motor arrangement which has a motor housing, in which a bearing point for the rotor is formed integrally on that side which points towards the hand piece coupling; on the opposite, that is to say “rear” side, a further, that is to say “rear” bearing flange is centered in the motor housing. DE 10 2007 048 340 A1 discloses a corresponding electric-motor arrangement, in which the bearing points are integrated directly into the stator body. The components for these known electric-motor arrangements are in part difficult to produce. Moreover, there is the risk of alignment errors with respect to the ideal motor axis, and the bearing seat can be deformed by thermal effects resulting from the motor coil and/or a sterilization, with the result that, furthermore, ball-bearing outer rings of the bearings are deformed and a bearing setting by springs fails. Both lead to an increase in running noise, vibrations and premature wear or failure.